Functional Event-Driven Architecture
Functional Event-Driven Architecture
Powered by Scala 3
About the Book
Explore the event-driven architecture (EDA) in a purely functional way. Learn to design and develop distributed systems that scale. Identify common design patterns in such systems.
In the same spirit of Practical FP in Scala, we will develop a distributed system written in Scala 3 that meets the requirements of a modern software architecture capable of processing billions of events per day at scale powered by Apache Pulsar and Fs2 streams.
The system also includes a Web Sockets service powered by Http4s, and two Web applications (one written in Elm; another in Scala.js), just for fun!
Although the application picks a particular design and implementation, the concepts should easily translate to other designs in the same space that can be built on top of Apache Kafka, Rabbit MQ, or other message brokers.
Additionally, essential reading material is recommended for those who wish to dive deeper into topics such as Distributed Systems, Streaming Systems, Event-Driven Applications, and Observability.
Have a look at the distributed system that supplements this book: https://github.com/gvolpe/trading
About the Author
Bundles that include this book
Table of Contents
- Preface
-
Acknowledgments
- People
- Software
- Fonts
-
Prerequisites
- Reading material
-
How to read this book
- Conventions used in this book
- Part I: Concepts
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1. Event-driven architecture
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1.1 Introduction
- 1.1.1 What problems does it solve?
- 1.1.2 When to use it? When not?
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1.2 Microservices architecture
- 1.2.1 Scalability
- 1.2.2 Fault tolerance
- 1.2.3 Observability
- 1.2.4 Versatility
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1.3 CQRS/ES
- 1.3.1 Commands
- 1.3.2 Queries
- 1.3.3 Reads & writes
- 1.3.4 When to use it? When not?
- 1.3.5 Frameworks
- 1.4 Summary
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1.1 Introduction
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2. Distributed systems
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2.1 Overview
- 2.1.1 Identifying points of failure
- 2.1.2 Consistency vs availability
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2.2 Idempotence
- 2.2.1 De-duplication
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2.3 Atomicity
- 2.3.1 Distributed transactions
- 2.3.2 Change data capture
- 2.3.3 Distributed locks
- 2.4 Summary
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2.1 Overview
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3. Stateless vs. Stateful
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3.1 Stateless services, stateful brokers
- 3.1.1 Stateful services
- 3.1.2 Application clustering
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3.2 Message-driven architecture
- 3.2.1 Delivery guarantees
- 3.2.2 Apache Kafka
- 3.2.3 Apache Pulsar
- 3.2.4 What should I use?
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3.3 State snapshots
- 3.3.1 Retention policy
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3.4 Schema evolution
- 3.4.1 Schema compatibility
- 3.4.2 Versioning strategies
- 3.4.3 Schema registry
- 3.5 Summary
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3.1 Stateless services, stateful brokers
- Part II: Coding
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4. Functional programming in Scala 3
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4.1 Domain modeling
- 4.1.1 Typeclass derivation
- 4.1.2 Newtypes
- 4.1.3 Refinement types
- 4.1.3 Orphan instances
- 4.2 Typeclasses
- 4.3 HTTP routes
- 4.4 Effectful context
- 4.5 Dependent types
- 4.6 Summary
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4.1 Domain modeling
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5. Effectful streams
- 5.1 Finite state machines
- 5.2 Resources and lifecycle
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5.3 Data pipelines
- 5.3.1 Real-time
- 5.3.2 Batching
- 5.3.3 Analytics
- 5.3.4 Data source
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5.4 Producer-consumer
- 5.4.1 In-memory via Queue
- 5.4.2 Distributed via Apache Pulsar
- 5.4.3 Distributed via Apache Kafka
- 5.5 Summary
- Part III: System
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6. Trading system (core services)
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6.1 Business requirements
- 6.1.1 Overview
- 6.1.2 Domain modeling
- 6.1.3 Shared modules
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6.2 Processor
- 6.2.1 Commands
- 6.2.2 Events
- 6.2.3 Command-event relationship
- 6.2.4 Entry point
- 6.2.5 FSM
- 6.2.6 Deep analysis
- 6.2.7 Scalability
- 6.2.8 Run
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6.3 Alerts
- 6.3.1 Datatypes
- 6.3.2 Event-alert relationship
- 6.3.3 FSM
- 6.3.4 Entry point
- 6.3.5 Scalability
- 6.3.6 Run
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6.4 Web Sockets
- 6.4.1 Datatypes
- 6.4.2 HTTP routes
- 6.4.3 Events handler
- 6.4.4 Unit tests
- 6.4.5 Entry point
- 6.4.6 Run
- 6.4.7 Scalability
- 6.4.8 Addendum
- 6.5 Summary
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6.1 Business requirements
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7. Trading system (alt services)
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7.1 Snapshots
- 7.1.1 Scalability
- 7.1.2 Entry point
- 7.1.3 FSM
- 7.1.4 Run
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7.2 Forecasts
- 7.2.1 Commands
- 7.2.2 Events
- 7.2.3 Command-event relationship
- 7.2.4 Engine
- 7.2.5 SQL store
- 7.2.6 Scalability
- 7.2.7 Entry point
- 7.2.8 Run
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7.3 Feed
- 7.3.1 Generators
- 7.3.2 Run
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7.4 Integration tests
- 7.4.1 Redis suite
- 7.4.2 SQL suite
- 7.5 Summary
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7.1 Snapshots
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8. Trading system (observability)
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8.1 Tracing
- 8.1.1 Distributed
- 8.1.2 Centralized
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8.2 Build & run
- 8.2.1 Docker compose
- 8.2.2 Continuous integration
- 8.2.3 Smoke tests
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8.3 Monitoring
- 8.3.1 Prometheus
- 8.3.2 Grafana
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8.4 Deployment
- 8.4.1 K8s cluster
- 8.4.2 Pods management
- 8.5 Summary
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8.1 Tracing
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9. Bonus: Web App
- 9.1 Entry point
- 9.2 Datatypes
- 9.3 View
- 9.4 Subscriptions
- 9.5 Updates
- 9.6 Build & run
- 9.7 Summary
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